There is already known, in particular from French patent application 2 834 662, to which corresponds US patent application 2005/0101235, French patent application 2 857 610, to which corresponds US patent application 2006/0154581, and French patent application 2 900 356, to which corresponds international application WO 2007/128894, a tool for surfacing an optical surface, the tool including: a rigid support having a transverse end surface; an elastically compressible interface attached to the rigid support, including a central part that is in line with to said end surface of the rigid support and a peripheral part that is transversely beyond said end surface of the rigid support; a flexible pad adapted to be pressed against a surface to be worked, attached to the interface on the opposite side to the rigid support, including a central part that is in line with said end surface of the rigid support and a peripheral part that is transversely beyond said end surface of the rigid support; and return spring means disposed between said rigid support and the peripheral part of said interface, the combination of said peripheral part of the pad, said peripheral part of the interface and the return spring means forming means for stabilizing the tool during surfacing, said tool being adapted to perform surfacing essentially in said central part of the pad.
To reduce the roughness of the optical surface, the tool is brought into contact with the optical surface and a sufficient pressure of the tool is maintained on it so that, by deformation of the interface, the pad espouses the shape of the optical surface.
While spraying the optical surface with a fluid, it is driven in rotation relative to the tool (or vice-versa) and is swept by the tool.
The optical surface is generally driven in rotation, friction between it and the tool being sufficient to entrain the tool so that it rotates with it.
The surfacing operation necessitates an abrasive that can be contained in the pad or in the fluid.
During surfacing, the interface, which is elastically compressible, compensates the curvature difference between the end surface of the tool support and the optical surface.
The results achieved by these tools are generally satisfactory, but it is sometimes difficult to avoid certain defects of appearance, namely the orange skin effect and the sheeplike effect.
To remedy these appearance defects, a flexible pad having a diameter larger than that of the interface so that the pad has an annular portion projecting transversely beyond the interface has already been proposed.
The resulting tool achieves an improvement in surface appearance, but in some circumstances such appearance defects remain.